In the petroleum process industry, it is common to use a fluidized bed reactor wherein solids are contacted with gases to promote chemical and physical reactions between the solids suspended in the gas and the gas passing therethrough. Fluidized bed reactors are typically used in catalytic cracking processes, petroleum coking and gasification processes and are contemplated for use in processes for the gasification of pulverized coal into low and medium BTU synthesis gas.
Typically, such fluidized bed reactors include a lower grid plate with a plurality of gas passageways therethrough to support the bed. Below such grid plate, it is conventional to have a plenum or wind box wherein the bed suspending gas is introduced under pressure to exit upwardly through the orifices in the grid plate to suspend the bed thereabove in a fluidized state. Unfortunately, as the reaction temperatures within the bed and the temperature of the fluidizing gas increases, the structural integrity of any metal grid used to support the bed is diminished and becomes the limiting factor on the upper temperature limit at which the process reaction may occur. An appreciation of these constraints in fluidized bed reactors may be obtained by reference to U.S. Pat. Nos. 4,226,830 and 4,159,305, whose disclosures are incorporated herein by reference for background. While in the latter patent an all ceramic material fluidized bed grid plate is contemplated, the substitution of the ceramic material therein for a prior art metallic grid does not eliminate the windbox pressure differential therebelow and therefore the structural forces created by the pressure differential in the windbox of U.S. Pat. No. 4,159,305 will greatly limit the operating temperature and pressure parameters of the fluid bed thereabove.